Hybrid inflators for vehicle airbags generally comprise a chamber storing a pressurized inert gas and a pyrotechnic adapted for discharge directed into the storage chamber. The hot gaseous products of pyrotechnic combustion enter the gas storage chamber and mix with the gas. The gas storage chamber has an exit opening which is covered by a rupturable seal, the seal being ruptured by mechanical action, by increased pressure or, in some instances, by action of the pyrotechnic itself. The inflation gasses are a mix of the stored gas and gaseous products of combustion of the pyrotechnic, with the stored gas being in part heated and expanded by the pyrotechnic. However, a certain portion of the stored gas generally flows from the storage chamber prior to being heated, thereby limiting the heat expansion of the stored gas.
One of the goals of a hybrid inflator is to reduce the volume of compressed gas which would be required for inflation of the vehicle airbag if pressurized gas alone were used. Another goal of the hybrid inflator is to reduce the amount of pyrotechnic required to inflate an airbag, at least in part to make the inflator more environmentally friendly. A further goal is to reduce particulate residue from operation of the airbag. These goals are achieved to a degree in present hybrid inflators, but further improvement in both of these areas is desirable.